generic_x86 builds don't need/use the sparse ext4 format.

Change-Id: I62973b131a728c3862be4642e2d49d0fa61555ac
Signed-off-by: Bruce Beare <bruce.j.beare@intel.com>
diff --git a/target/board/generic_x86/BoardConfig.mk b/target/board/generic_x86/BoardConfig.mk
index f906570..2268d41 100644
--- a/target/board/generic_x86/BoardConfig.mk
+++ b/target/board/generic_x86/BoardConfig.mk
@@ -22,6 +22,7 @@
 BOARD_FLASH_BLOCK_SIZE := 512
 BOARD_USERDATAIMAGE_PARTITION_SIZE := 50M
 BOARD_INSTALLERIMAGE_PARTITION_SIZE := 500M
+TARGET_USERIMAGES_SPARSE_EXT_DISABLED := true
 
 
 # The eth0 device should be started with dhcp on boot.